The research proposed in this renewal application is a continuation of originally proposed research which is an attempt to examine the composition of the extracellular fluid compartment of the brain, to determine which, if any, biogenic amines are involved in the behavioral action of drugs of abuse. Operant conditioning techniques are employed to study the dependent behavioral variables because they offer a good control for determining if brain perfusion itself affects CNS function and because the experimentor can objectively and automatically control and analyze behavior. This Proposal will also test several hypotheses regarding the reinforcing consequence of behavior engendered by the withdrawal state and determine if acute stimulant administration to opiate dependent rats has a differential effect upon animals who are dominant versus animals who are submissive members of a paired social hierarchy. The involvement of various monoamine transmitters and Ca ions in behavioral consequences of amphetamine, cocaine and/or opiate withdrawal will be examined.